1. Field of the Invention
The present invention relates to a process of polymerizing certain aromatic dianhydrides to form selected poly(dianhydride) compounds. The present invention also relates to a method of making selected poly(dianhydride) compounds terminated with reactive end groups. The present invention further relates to a process of making selected poly(amic acid) compounds and selected poly(amic acid) compounds terminated with reactive end groups both of which are based on said selected poly(dianhydride) compounds. Still further, the present invention relates to a process of producing selected poly(imide) compounds and selected poly(imide) compounds terminated with reactive end groups, both of which are based on selected poly(dianhydride) compounds. In addition the present invention relates to a method of seperating and purifying the polymer products herein described.
2. Brief Description of Related Art
Dianhydrides are known precursors to many chemical products, including poly(amic acids) and poly(imide) resins. See, for example, C. E. Sroog, J. Polymer Science, Macromolecular Reviews, 11, 161 (1976). Known dianhydrides include 1,2,4,5-benzene tetracarboxylic dianhydride (CAS No. 89-32-7) also known as pyromellitic dianhydride (PMDA) which has formula (A): ##STR3##
Other known dianhydrides include those in the general formula (B): ##STR4## wherein R is an organic or inorganic linking group.
It is known to react dianhydrides with epoxides to form thermoset systems. It is also known to react dianhydrides with diamines to form poly(amic acids). For example, see the Sroog article cited above.
Also, it is known to convert poly(amic acids) into poly(imide) resins. See U.S. Pat. No. 4,480,088 which issued to Pike on Oct. 30, 1984.
It is also known to react poly(imides) with polymerizable end groups having amino functionalities to form poly(imides) terminated with reactive end groups. See, for example, U.S. Pat. No. 3,845,018 which issued to N. Bilow, A. L. Landis, and L. J. Miller on Oct. 29, 1974.
It is also known that poly(imides) and poly(imides) terminated with reactive end groups have utility as adhesives. See, for example, A. K. St. Clair and T. L. St. Clair "The Development of Aerospace Polyimide Adhesives" in Polyimides, K. L. Mittal, Ed. Vol. 2, Plenum Press, New York (1984).
It is also known to dimerize anhydrides to form bislactones are different in chemical structure from dianhydrides. See F. Ramirez, H. Yomanaka, and O. H. Basedow Journal of American Chemical. Soc., 83, 173 (1961).
There is still a need for better high temperature epoxy systems which can be used as adhesives and composite matrices (e.g., composites used in aerospace applications). It is believed that the poly(dianhydrides) of the present may be suitable curatives for these epoxy systems.
There is also a need for better rigid-rod resin systems (i.e., where the resin structure has limited flexibility) to provide better strength to adhesives and composite matrices. It is believed that the poly(dianhydrides) with reactive end groups of the invention may solve this need for some applications.
There is also a need for resin systems which have a rigid rod portion and a flexible portion to provide both strength and flexibility to adhesives and composite matrices.
There is also a need for poly(imide)-type polymers which are more thermally stable and have more strength than the conventional ones made by dianhydrides and diamines. It is believed that the poly(imides) and poly(imides) with reactive end groups provide better thermal stability and better strength.